Current drill bits usually work well in applications or drilling environments where a single formation or rock type (e.g., salt, sediment, carbonate) is encountered in the interval or hole size to be drilled. However, some applications or down-hole environments have layers or zones of different formation and lithology types in the same interval or hole size. For example, a down-hole environment may have a first layer of salt and a second layer of sediment in the same interval. In order to drill through a zone comprising layers of different rock types, the drill bit, bottom hole assembly, and/or other parts of the drill string may need to be changed when transitioning between the different layers or zones, as the different rock types may require different drilling parameters that may not currently be accommodated by the same drill bit. For example, when drilling in a zone having a salt layer and a sediment layer, one type of drill bit may be needed to drill through the salt layer and a different type of drill bit may be needed to drill through the sediment layer. In order to change the drill bit or other parts of the drill string amid an operation, the drill string and bottom hole assembly (BHA) must be tripped thus taken out of the hole and, then run back into the hole after the tool(s) are changed. Variations in the type, hardness and abrasiveness of the rock layers can further increase the complexity of the drilling operation, with compromising effects on drilling process efficiency and overall project costs. Typically, the more complex the drill zone, the more frequently the drill string will need to be tripped. Tripping, when unplanned, is a costly procedure which is to be minimized.
As an additional challenge, bottom hole assembly (BHA) components have operational time limitations, which also tend to be influenced by dynamic conditions. This characterization is usually quantified and expressed on a time scale as mean time between failures (MTBF). During a drilling operation, it may be advantageous to trip the drill string and change or recondition the equipment before the mean time between failure is reached, thereby decreasing the likelihood that the equipment will fail during the operation when the tools and equipment are downhole. Thus, it is desirable to drill through the required interval before the mean time between failure runs out. However, and as an example, if a drill bit does not exhibit appropriate durability and stability characteristics, to facilitate achievement of high enough rate of penetration (ROP), especially in the layered formations described, to drill through the required interval, before MTBF limitations are reached, the drill string will need to be tripped.